#include <stdio.h>

int main(){
    int number;
    begin:printf("输入数字:");
    while(1)
    {
        scanf("%d",&number);
        if(number<=0||number>100)
        {
            printf("凉了\n");
            break;
            }
        switch(number/10)
        {
            case 10:
            {
                printf("A\n");
                goto begin;
                free;
            }
            case 9:
            {
                printf("B\n");
                goto begin;
                free;
            }
            case 8:
            {
                printf("C\n");
                goto begin;
                free;
            }
            case 7:
            {
                printf("D\n");
                goto begin;
                free;
            }
            case 6:
            {
                printf("E\n");
                goto begin;
                free;
            }
            default:printf("F\n");goto begin;free;
        }
    }
}
